Control systems for switching power converters typically process a feedback signal from the converter with a digital or analog low-pass filter prior to using the feedback signal for a closed-loop control algorithm. Filtering the feedback signal, however, may increase the system response time and introduce noise, distortion and/or instability, etc. This degradation of system performance may be especially problematic in applications where the power converter is required to generate output waveforms having large dynamic range and/or bandwidth, or where large, unpredictable transients must be accommodated. For example, in applications where a battery, photovoltaic (PV) panel, fuel cell, or other DC power source must be coupled to an AC power grid, an inverter may be required to generate a 120 Hz rectified sine wave output current which is then converted to an AC sine wave through a bridge circuit. The rectified sine wave has sharp reversals (valleys) in the waveform which require a control loop having a very high bandwidth to accurately generate this waveform. Low-pass filtering the feedback signal, however, reduces the bandwidth and may result in rounding of the waveform valleys and/or other adverse effects caused by insufficient control loop bandwidth.
Random pulse width modulation (RPWM) may be used to reduce electromagnetic interference (EMI) from switching power converters. With RPWM, the switching frequency of the power converter is varied randomly to spread the spectrum of the switching noise, thereby reducing peaks at the primary switching frequency and harmonics thereof. Thus use of randomized switching frequencies in RPWM system introduces additional complications relating to the synchronization of the sampling with the switching which has implications for control loop bandwidth. Even in RPWM systems, however, the samples are typically low-pass filtered, thereby reducing the control loop bandwidth and causing degradation of system performance.